Hey guys i realy hope someone can help me out here. I have a pair of Event ASP8 studio monitors that werd made in 2005 and one of them stopped working out of the blue recently. These speakers are self powered with 300 watt built in amplifiers. I opened it up and the only thing i could notice wrong was one of the 4 op amps marked LM3886TF was burnt. It is actualy cracked down the middle and the contacts are black and melted. All of the surface mount resistors and the capacitors appear to b perfect the only other thing i noticed was there was very very little thermal pasteon the op amps and the heatsink and what is there is dried up. These speakers get very hot to the point of not being able to touch them so is it possible that improper heat dispertion fried the op amp or is there something else going on here. I ordered a new op amp and if i replace it do i run the risk of having it burn up again right away? Or should it b ok if i reapply thermal paste considerably on everything that needs it? Basicaly im wondering what could cause this to happen and should i b ok by jus replacing the op amp wich is the only burnt component on the board. Any help would realy b appreciated this is my first post and i am a self taught electronics fixer but my track record has been pretty good so far with what i have repaired so i would love as much information on this as possible. Thanks again to anyone who choses to help me out!
Hi!
As Andrew tries to say I guess, divide your text in to smaller pieces so it will be more easy to read.
Anyway, here is a link to the schematic: Event ASP8 Service manual
For start, which one of the LM3886 is broken?
As Andrew tries to say I guess, divide your text in to smaller pieces so it will be more easy to read.
Anyway, here is a link to the schematic: Event ASP8 Service manual
For start, which one of the LM3886 is broken?
Thank you for the download. Any and all information on this topic is very appreciated. My main question is will replacing this op amp fix this amp if there is no other burn out components or damaged solder leads? I know without testing everything on the board it is basicly a crap shoot but is it possible that this chip fried all on its own without anything else damaged before or after it on the board?
LM3886 shuts itself off when it reaches dangerous temperature.
There should be another problem.
That sounds good thank you but where do i connect the bulb to? The op amp directly ? I am an electrician by trade but i am new to electronics. I rebuilt a few things the last being i changed the chips and a few capacitors on a technics 1200 turntable and got it working but i generaly dont know too much about circuit boards. I catch on pretty quick though so if u could please jus breifly describe wat to put where i can usualy figure it out. Thank you all so much for taking the time to help me.
Ok good.
First, I have cracked some LM3886 in the past due to oscillation.When they oscillated and got broken they where cracked and burnt on the legs, so my guess is that it has oscillated somehow.
Oscillation can happen due to a different number of reasons. One thing I noticed in the schematic is R18, a trim-pot connected to the inverted input of the LM3886. It look's like it's there to adjust the DC-offset of the LM3886.
I would suggest that you replace the broken LM3886, connect a bulb-tester as suggested, but before starting it up, disconnect the speaker connected to U1. Add power, use a volt-meter and measure (DC) on the output of the LM3886, it should not be greater than 100mV, preferably under 50mV. You should be able to reduce the DC-offset by turning R18. Try to get as close to 0 as possible.
First, I have cracked some LM3886 in the past due to oscillation.When they oscillated and got broken they where cracked and burnt on the legs, so my guess is that it has oscillated somehow.
Oscillation can happen due to a different number of reasons. One thing I noticed in the schematic is R18, a trim-pot connected to the inverted input of the LM3886. It look's like it's there to adjust the DC-offset of the LM3886.
I would suggest that you replace the broken LM3886, connect a bulb-tester as suggested, but before starting it up, disconnect the speaker connected to U1. Add power, use a volt-meter and measure (DC) on the output of the LM3886, it should not be greater than 100mV, preferably under 50mV. You should be able to reduce the DC-offset by turning R18. Try to get as close to 0 as possible.
Capacitors
This test circuit looks good and handy. I have a PYE radio that stood unused for 30 years and the moment I got it I needed a tuning cap for a antenna tuner. I then just for old time sake powered the chassis up AND IT PLAYED no problem! Is this just a fluke or were those caps used on transistor sets of inferior quality as those old sets? Mine was made in September 1950 that's right 62 years ago and she sounds better than new sets of today? Just one question I found those old Mullard PYE and Philips sets WITH ONE LOUDSPEAKER MOUNTED DIRECT ON A PLANK SEALING IT OFF!!:
This test circuit looks good and handy. I have a PYE radio that stood unused for 30 years and the moment I got it I needed a tuning cap for a antenna tuner. I then just for old time sake powered the chassis up AND IT PLAYED no problem! Is this just a fluke or were those caps used on transistor sets of inferior quality as those old sets? Mine was made in September 1950 that's right 62 years ago and she sounds better than new sets of today? Just one question I found those old Mullard PYE and Philips sets WITH ONE LOUDSPEAKER MOUNTED DIRECT ON A PLANK SEALING IT OFF!!:
Hi, I have Event TR8 speakers which are pretty similar to the ASP8.
The same thing happened to me, chip amp blew.
Luckily the drivers were ok.
I eventually went for Tripath amps mounted externally along with a digital active XO, and they are up and running again, and they sound smoother now also which is nice.
If you do replace your amp chip, consider upgrading the heatsink as Event seem to be cutting corners here.
The same thing happened to me, chip amp blew.
Luckily the drivers were ok.
I eventually went for Tripath amps mounted externally along with a digital active XO, and they are up and running again, and they sound smoother now also which is nice.
If you do replace your amp chip, consider upgrading the heatsink as Event seem to be cutting corners here.
I'm having a related issue with an SP8 amp, although my LM3886 may not yet be fried. When checking DC on the output, is this at the speaker leads, disconnected from the driver? If so, I'm getting 1.1 V but this does not move when I adjust pot R18. U1 runs hot and is crackly when I adjust HF trim R10 (this may be because there is DC across R10 pot). Maybe one of the components near R18 is bad/open?
I notice the spec sheet calls out TI/NatSemi but chip has JM65RA on it, I suspect they used a cheaper substitute.
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